Electric vehicles, hybrid vehicles, fuel cell powered vehicles and other similar vehicles configured to be capable of generating force via an electric motor to drive the vehicle have a power storage device mounted therein to store power to drive the electric motor. When such a vehicle is started, accelerated or the like, the power storage device supplies the motor with power to generate force to drive the vehicle, whereas when the vehicle travels downhill, is decelerated or the like, the motor's regenerative braking generates power which is in turn supplied to the power storage device.
For such a vehicle, there has been proposed a configuration electrically connectable to a commercial power grid or a similar power supply external to the vehicle (hereinafter also simply referred to as an “external power supply”) to electrically charge the power storage device (hereinafter also simply referred to as external charging). For example, a so called plug-in hybrid vehicle is known that allows an electrical outlet provided in premises to be connected to the vehicle's charging port via a charging cable to allow the power storage device to be electrically charged from a power supply of an ordinary household. This can increase the hybrid vehicle's fuel consumption efficiency.
For such an externally chargeable vehicle, a concept has been discussed to consider the vehicle as a power supply source to supply power from the vehicle to a load external to the vehicle, as seen in the smart grid.
For example, Japanese Patent Laying-Open No. 2010-154637 (Patent Document 1) discloses a power supply system allowing a power supply equipped vehicle and premises to be connected via a power supply cable and thereby bidirectionally supply power therebetween. Patent Document 1 describes that the vehicle is provided with a controller to control supplying power. The vehicular controller communicates with that of the premises by superimposing data on a power line including the power supply cable. When the vehicle is connected to the premises via the power supply cable, the vehicular controller switches plug-out power supply which supplies power from a vehicular power supply to the premises and plug-in power supply which supplies power from a power supply for the premises to the vehicle, as based on a voltage of a commercial power supply in the premises transmitted from the controller of the premises, the vehicular power supply's state of charge, and the like.